Method and system for navigating within a flexible organ of the body of a patient

ABSTRACT

Method for navigating a flexible medical device within a flexible organ of the body of a patient, toward a target region of interest of an inner wall of the flexible organ, by employing a previously acquired global three-dimensional (3D) model of the flexible organ, the method including the procedures of acquiring an initial stereoscopic image of an initial region of the flexible organ and reconstructing an initial local 3D model of the initial region according to the initial stereoscopic image, identifying and registering the initial local 3D model with an initial segment of the previously acquired global 3D model, acquiring a successive stereoscopic image of a successive region of the flexible organ and reconstructing a successive local 3D model of the successive region according to the successive stereoscopic image, identifying and registering the successive local 3D model with a successive segment of the previously acquired global 3D model, detecting the target region of interest by identifying a topography of the target region of interest according to the previously acquired global 3D model in the successive local 3D model, and producing a notification to indicate that the target region of interest is detected when the target region of interest is detected.

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to medical devices in general, and to methods and systems for navigating within a colon of a body of a patient, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

The colon is a part of the intestine, extending from the small intestine to the rectum. The colon is primarily responsible for extracting water from digestive waste. The colon is a flexible organ, and undergoes deformations and forms changes with time. Such deformations may include, for example, stretching, contracting, twisting, and the like. Colon cancer is a major cause of death throughout the world. Early detection of malignant tumors, which manifest themselves initially as polyps or cysts in the colon, can greatly improve the chances of recovery of a diagnosed patient.

Stereoscopic imaging of the colon (i.e., stereoscopic colonoscopy) presents a challenge due to the flexible and constantly-changing nature of the colon. Deformations of the colon make it difficult to retrace particular areas of the colon, at different times. If a physician identifies an abnormal feature in a colon of a patient (e.g., a polyp), then the physician may wish to further examine that abnormal feature at a later time, in order to follow its development. However, it may be difficult for the physician to locate the same feature of the colon, due to the deformation undergone by the colon. Stereoscopic image detection devices, used in colonoscopy, are known in the art. Known colonoscopy devices also employ systems and methods for determining the spatial position of the medical device relative to a known reference system.

U.S. Pat. No. 6,167,296 issued to Shahidi, and entitled “Method for Volumetric Image Navigation”, is directed to a navigation system for a surgical procedure. The navigation system includes a set of fiducial markers, a surgical probe, a computer, a display device, a sensing unit, and a set of two light emitting diodes (LEDs).

The fiducial markers are attached to a head of a patient. The computer is connected with the display device, the sensing unit and with the surgical probe. The LEDs are connected with the surgical probe. The sensing unit is mounted above an operating table, on which the surgical procedure takes place.

The locations of the fiducial markers are the same as their locations at a previous time of acquiring a three-dimensional image of the head of the patient. The three-dimensional image of the head is acquired previously, by Magnetic Resonance Imaging (MRI). The computer stores the MRI image of the head, in a memory thereof. The computer generates a three-dimensional model from the MRI image. The fiducial markers allow alignment of the position and orientation of the head, such that it is the same at the time of the surgical procedure, as it was when the MRI image was acquired.

A surgeon directs the surgical probe toward a tissue of interest in the head of the patient. The LEDs emit infrared pluses. The sensing unit senses the infrared pulses. The computer controls the timing and synchronization of the infrared pulses, and the recording and processing of the infrared pulses received by the sensing unit. The computer processes the infrared pulses to generate data indicating the location and orientation of the surgical probe in real time, and records this data. The computer displays on the display device, a three-dimensional image of the head of the patient, respective of the position and orientation of the surgical probe.

U.S. Pat. No. 6,226,543 issued to Gilboa et al., and entitled “System and Method of Recording and Displaying in Context of an Image a Location of at Least One Point-Of-Interest in a Body During an Intra-Body Medical Procedure”, is directed to a system for simultaneously obtaining location data of a body of a patient, location data of a catheter inserted into the body, and location data of an imaging instrument. The system is used for imaging the catheter and the body, and recording that data. The system includes an imaging instrument, a catheter, a locating implement, a location implement, a computer, and a monitor.

The computer is connected with the monitor, the imaging instrument and with the locating implement. The location implement is a transmitter which emits electromagnetic waves, positioned at the tip of the catheter. The locating implement is a receiver which receives electromagnetic waves, located above the operation table, within an effective distance with respect to the location implement. The body is fixed at a known location during the procedure (i.e., on the operating table). The imaging instrument is located above the operation table.

A surgeon inserts the catheter into a portion of the body of the patient. The surgeon employs the imaging instrument for imaging of that portion of the body. The surgeon advances the tip of the catheter to a point-of-interest in that portion of the body. The locating implement locates the location implement, and the computer records the location of that point. The point-of-interest is projected and displayed on the monitor, in relation with the respective location of the body and with the respective location of the imaging instrument. Thus, the surgeon can locate the point-of-interest, recorded at a previous time, when the imaging instrument was positioned differently relative to the operating table.

U.S. Pat. No. 5,902,239 issued to Buurman, and entitled “Image Guided Surgery System Including a Unit for Transforming Patient Positions to Image Positions”, is directed to a system for guided surgery using a camera and a plurality of LEDs. The system includes two cameras, a plurality of LEDs, a computer, a surgical instrument, a plurality of fiducial markers and a monitor.

The computer is connected with the monitor and with the cameras. The LEDs are positioned on the surgical instrument. The locations of the fiducial markers are substantially the same as their locations at a previous time of acquiring a Computed Tomography (CT) image of the patient. The computer contains the CT image. The cameras are sensitive to the light emitted by the LEDs. The computer receives image signals from the cameras. The computer computes the position of the surgical instrument relative to a body of the patient, according to the image signals acquired by the cameras. A surgeon indicates the location of the fiducial markers, by pointing at the fiducial markers with the surgical instrument. The computer computes the corresponding position of the fiducial markers in the CT image, and in the current images acquired by the cameras. The computer computes a transformation matrix for transforming each point in a reference coordinate system of the current images, to a reference coordinate system of the CT image. The computer computes the corresponding position of the surgical instrument in the CT image reference coordinate system. The computer displays, on the monitor, a superimposed image of the surgical instrument in the CT image.

U.S. Pat. No. 6,923,768 issued to Camus et al., and entitled “Method and Apparatus for Acquiring and Displaying a Medical Instrument Introduced into a Cavity Organ of a Patient to be Examined or Treated”, is directed to a system for recognizing the position of a treatment or examination device. The system includes a treatment apparatus, a control and processing device (CPD), an ultrasound acquisition device, a plurality of position sensors, a position acquisition system, a medical instrument and a monitor.

The CPD is connected with the ultrasound acquisition device, the position acquisition system and with the monitor. One of the position sensors is integrated into the ultrasound acquisition device and another position sensor is integrated into the medical instrument.

A physician displaces and turns the ultrasound acquisition device in a cavity organ of a patient, in order for the ultrasound acquisition device to acquire two-dimensional (2D) ultrasound images of the interior of the cavity organ. The position acquisition system acquires the spatial position and orientation of the ultrasound acquisition device, in the coordinate system of the position acquisition system. The CPD generates a three-dimensional (3D) ultrasound image dataset on the basis of the 2D ultrasound images. The CPD generates a 3D reconstruction image, according to the 3D ultrasound image dataset. The resolution of the 3D ultrasound image dataset grows as the number of acquired 2D ultrasound images grows. The position acquisition system acquires the position of the medical instrument in a coordinate system of the position acquisition system. The CPD displays on the monitor, the 3D reconstruction image and the respective position of the medical instrument.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a schematic illustration of a system for navigating a flexible medical device within a flexible organ of the body of a patient, constructed and operative in accordance with an embodiment of the disclosed technique;

FIG. 2 is a schematic illustration of a section of a previously acquired global 3D model of an inner wall of the flexible organ of FIG. 1;

FIG. 3 is a schematic illustration of a local 3D model of the inner wall of a region of the flexible organ of FIG. 1, constructed during a medical operation on the body of the patient;

FIG. 4 is a schematic illustration of a local 3D model of a region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model;

FIG. 5 is a schematic illustration of another local 3D model of another region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model;

FIG. 6 is a schematic illustration of a further local 3D model of a further region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model; and

FIG. 7 is a schematic illustration of a method for operating the system of FIG. 1, operative according to another embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by identifying a plurality of topographical features of an inner wall of a colon of the body of a patient, according to a global three-dimensional (i.e., 3D) model of the colon acquired prior to a colonoscopy, as a user advances a stereoscopic endoscope within the colon, toward a target region of the colon. During the colonoscopy, a stereoscopic image acquisition device located at the tip of the stereoscopic endoscope, acquires a stereoscopic image of the inner wall of the colon.

An image processor reconstructs a local 3D model of the inner wall of the colon, in real-time, according to the stereoscopic image acquired by the stereoscopic image acquisition device. As the user advances the stereoscopic endoscope within the colon, the image processor examines each local 3D model in succession, in order to confirm that each local 3D model of the respective region of the colon, matches the segment respective of that region, within the previously acquired global 3D model. In case the image processor identifies the local 3D models, the user receives no cue from the image processor, thereby confirming that she is guiding the stereoscopic endoscope in the correct direction, and hence continues to advance the stereoscopic endoscope toward the target region. In case the image processor fails to identify a local 3D model, the image processor produces an output via a user interface, to initiate a change in direction of movement of the stereoscopic endoscope, so that the image processor succeeds to identify the local 3D model respective of that region. Once the image processor identifies the local 3D model, the user can continue to advance the stereoscopic endoscope further toward the target region. When the image processor identifies the local 3D model respective of that region of the colon, the image processor also checks the topography of that region, according to the global 3D model, in order to determine whether the tip of the stereoscopic endoscope is located at the target region. In case the tip of the stereoscopic endoscope has reached the target region, the image processor produces an output via the user interface, to notify the user accordingly.

The position and orientation of the topographical features of the inner wall of the colon at the time of the colonoscopy, can be different than those at the time of mapping of the inner wall of the colon prior to the colonoscopy. This is due to dilatation and contraction of the colon, as well as changes in axial dimensions thereof. For this purpose, the image processor performs transformation and rotation operations on each of the local 3D models, as well as modifying the scale of each of the local 3D models, in order to identify the local 3D model within the previously acquired global 3D model.

Reference is now made to FIGS. 1, 2, and 3. FIG. 1 is a schematic illustration of a system, generally referenced 100, for navigating a flexible medical device within a flexible organ of the body of a patient, constructed and operative in accordance with an embodiment of the disclosed technique. FIG. 2 is a schematic illustration of a section of a previously acquired global 3D model of an inner wall of the flexible organ of FIG. 1. FIG. 3 is a schematic illustration of a local 3D model of the inner wall of a region of the flexible organ of FIG. 1, constructed during a medical operation on the body of the patient.

With reference to FIG. 1, system 100 includes a flexible medical device 102, a stereoscopic image acquisition device 104, an image processor 106, and a user interface 108. Stereoscopic image acquisition device 104 is located at the tip of flexible medical device 102. Flexible medical device 102 can be for example, a stereoscopic endoscope, a stereoscopic colonoscope, and the like. Stereoscopic image acquisition device 104 is an optical device which acquires a stereoscopic image of an object (not shown). For this purpose, stereoscopic image acquisition device 104 can include a plurality of optical elements, such as lenses (not shown), objective (not shown), an aperture stop (not shown), a charge-coupled device (CCD, not shown), a complementary metal-oxide semiconductor (CMOS, not shown), and the like. User interface 108 can be an audio device (e.g., loudspeaker), visual device (e.g., display), tactile device (i.e., haptic device), and the like. Image processor 106 is coupled with stereoscopic image acquisition device 104 and with user interface 108.

In the example set forth in FIG. 1, flexible medical device 102 is a stereoscopic colonoscope which is inserted into a colon 110 of a body (not shown) of a patient (not shown). Alternatively, flexible medical device 102 can be an endoscope to examine the interior of an esophagus of a patient. Further alternatively, flexible medical device 102 can be a bronchoscope in order to examine the interior of the bronchi of the patient. Flexible medical device 102 can further be a medical device for examining another volumetric flexible organ, such as a small intestine, a urinary tract (i.e., a cystoscope), a kidney (i.e., a nephroscope), a uterus, a stomach (i.e., a gastroscope), a spinal canal, a blood vessel, a joint (i.e., an arthroscope), and the like. When flexible medical device 102 is employed to examine the inner wall of a blood vessel, stereoscopic image acquisition device 104 can be a near Infrared (IR) camera. Colon 110 includes an ascending colon 112, a transverse colon 114, and a descending colon 116. Ascending colon 112 connects to a small intestine (not shown) of the body of the patient. Descending colon 116 connects to a rectum (not shown) of the body of the patient, through a rectal ampulla 118. The rectum includes an anus 120.

A user (not shown) attempts to navigate flexible medical device 102 within colon 110, which is inserted through the rectum, in order to reach a target region of interest 122 within transverse colon 114. For this purpose, the user employs system 100 to construct a global three-dimensional (i.e., 3D) model of transverse colon 114 and descending colon 110, during an imaging session prior to the medical operation on the body of the patient. Alternatively, the global 3D model can be constructed by employing another imaging system, similar to system 100.

The user advances flexible medical device 102 through descending colon 116 and transverse colon 114, and while pulling back flexible medical device 102 from colon 110, enables stereoscopic image acquisition device 104 to acquire a stereoscopic image (not shown), of an inner wall 124 of colon 110. Alternatively, stereoscopic image acquisition device 104 can acquire the stereoscopic image in a forward movement of flexible medical device 104 within colon 110. As the user advances flexible medical device 102 through colon 110, a length indicator (not shown) can determine the length of flexible medical device 102, which has already been advanced through colon 110. The length indicator can further inform the user of this length, in order to avoid looping of flexible medical device 102 within colon 110.

The stereoscopic image includes at least two two-dimensional images of inner wall 124. The stereoscopic image can include for example, a two-dimensional right view image and a two-dimensional left view image of inner wall 124. Alternatively, the stereoscopic image can include four two-dimensional images of inner wall 124, from four different viewpoints (e.g., right, left, below, and above).

Image processor 106 reconstructs a global 3D model (not shown) of colon 110, according to the stereoscopic images. The global 3D model is a video image. Inner wall 124 of colon 110 includes a plurality of topographical features 126 (e.g., protrusions and depressions). Image processor 106 reconstructs global 3D model according to topographical features 126. An initial local 3D model (not shown) respective of topographical features 126, located at an initial region of colon 110 (i.e., anus 120), which is reconstructed during the medical operation on the body of the patient, remains substantially the same at the time of the medical operation on the body of the patient. The initial region of colon 110 can thus be used as a visual anchor, in identifying the local 3D model with a respective initial segment of the global 3D model. Alternatively, another region of colon 110, having a substantially permanent geometry and topography, can be used as the visual anchor. This is due to the fact that generally no dilatation or contraction, nor changes in axial dimensions occur in the region of anus 120, since the imaging session, and due to the fact that anus 120 is firmly coupled to the body of the patient.

Image processor 106 reconstructs this initial local 3D model, according to a stereoscopic image which stereoscopic image acquisition device 104 acquires from anus 120, during the medical operation on the body of the patient. Image processor 106 stores this initial local 3D model in a memory (not shown). During the imaging session, the user indicates the location of target region of interest 122, via user interface 108, thereby enabling image processor 106 to store a topography (not shown) respective of target region of interest 122, in the memory, as it appears in the global 3D model.

With reference to FIG. 2, a segment 150 of a region 152 within colon 110, in the global 3D model, is characterized by a plurality of relations between topographical features 154, 156, 158, 160, and 162. These relations can include for example, the mutual distances between topographical features 154, 156, 158, 160, and 162, the orientation, size, or a combination thereof, of each of topographical features 154, 156, 158, 160, and 162, and the like.

When the user inserts flexible medical device 102 into colon 110 through anus 120, stereoscopic image acquisition device 104 constantly acquires a stereoscopic image of inner wall 124. Image processor 106 produces a real-time 3D video image (not shown), during the medical operation, according to the stereoscopic image which stereoscopic image acquisition device 104 acquires. There is substantially no change in the 3D geometry of the rectum and anus 120. Hence, image processor 106 can identify the initial local 3D model at anus 120, and register this initial local 3D model with the anus 120 (i.e., the initial region of colon 110), of the global 3D model of inner wall 124. As the user advances flexible medical device 102 within colon 110, stereoscopic image acquisition device 104 successively acquires a stereoscopic image (not shown) from inner wall 124, and image processor 106 reconstructs successive local 3D models (not shown), according to the stereoscopic image, in real-time. Each of these local 3D models includes a group of topographical features 126. Image processor 106 can also analyze the successive local 3D model, to determine the size and shape of certain topographical features 126, in order to assist the user in determining whether those topographical features 126 may require further examination or treatment (e.g., polyps or cysts).

With reference to FIG. 3, during the medical operation, the 3D geometry of colon 110 has changed relative to the one at the imaging session (FIG. 2). For example, the orientation of each of topographical features 154, 156, and 160 has changed, and the relative location of topographical features 158, 160, and 162 has changed, and the location of each of topographical features 156, 160, and 162 has changed. A local 3D model of a region 190 of colon 110, which is based on topographical features 154, 156, 158, 160, and 162, is referenced 192.

Local 3D model 192 is a local 3D model successive to the initial local 3D model. Image processor 106 tries to identify local 3D model 192, according to the global 3D model, despite the changes in the 3D geometry of colon 110. For this purpose, image processor 106 performs image transformation and rotation operations on local 3D model 192, until image processor 106 identifies local 3D model 192. Due to this change in geometry, there is a difference in image scale and orientation between those of local 3D model 192, and those of the respective portion of region 190 of segment 150 of global 3D model. For this purpose, image processor 106 sets the scale of local 3D model 192 to different values, until image processor 106 identifies and registers local 3D model 192 with the global 3D model.

In case image processor 106 identifies local 3D model 192, image processor 106 produces no output, and the user continues to advance flexible medical device 102 toward target region of interest 122. In case image processor 106 fails to identify local 3D model 192, image processor 106 produces an output via user interface 108, to direct the user to move flexible medical device 102 toward a selected direction. Image processor 106, then performs the above procedure for a local 3D model respective of a new region within colon 110, until local 3D model 192 is identified and registered. The user then advances flexible medical device 102 further on toward target region of interest 122.

Once image processor 106 identifies and registers local 3D model 192, image processor 106 checks whether the topography of region 190 matches that of target region of interest 122. In case the outcome is positive, image processor 106 notifies the user that the tip of flexible medical device has reached target region of interest 122, directs a display (not shown) coupled with image processor 106, to display target region of interest 122.

It is noted, that image processor 106 performs the above procedure at a substantially high rate (e.g., up to 30-50 times per second), such that the relative scaling between successive local 3D models are substantially small. Hence, image processor 106 modifies the scale of each local 3D model, within a predetermined range (e.g., ±5%), relative to the preceding local 3D model.

Image processor 106 can also analyze the respective local 3D model of target region of interest 122, in order to assist and guide the user with various operations, to be performed within target region of interest 122 (e.g., resection of certain topographical features of colon 110). Image processor 106 can further identify certain hidden topographical features of colon 110, detected in the successive local 3D model, and direct the user toward these features. Image processor 106 can also identify certain topographical features 126 in the local 3D model (either automatically or manually), and compare the size and shape of those features with the same features, as they appear in the respective segment of the global 3D model. For example, if a certain topographical feature 126 is found to have grown abnormally relative to the global 3D model, image processor 106 can produce a notification to the user, directing her to that certain topographical feature 126, for further examination or operation.

The system can include a moving mechanism (not shown) coupled with the image processor. This moving mechanism moves the flexible medical device within the colon, according to an output which the image processor produces, thereby obviating the need for the user.

Reference is now made to FIGS. 4, 5, and 6. FIG. 4 is a schematic illustration of a local 3D model of a region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model. FIG. 5 is a schematic illustration of another local 3D model of another region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model. FIG. 6 is a schematic illustration of a further local 3D model of a further region of the colon of FIG. 1, wherein this local 3D model includes a portion of the topographical features of a segment in the global 3D model, which corresponds with this region, and which is supposed to match this local 3D model.

With reference to FIG. 4, a local 3D model of a region 220 of colon 110, which is based on topographical features 154, 158, 162, 222, and 224, is referenced 226. In order to enable the user to advance flexible medical device 102 within colon 110, toward the next region of colon 110, image processor 106 has to identify and register local 3D model 226, with the global 3D model.

At this stage, image processor 106 employs a search algorithm known in the art, for seeking a match between segment 150 (FIG. 2) of the global 3D model, and respective of region 152, and a local 3D model in region 220. Local 3D model 226 includes topographical features 154, 158, 162, and 222 in their entirety, a partial portion of topographical feature 224, and excludes topographical features 156 and 160. It is noted, that the local 3D model in region 220 has to include topographical features 154, 158, and 162, topographical features 156 and 160 (which are missing from local 3D model 226), and exclude topographical features 222 and 224.

By referring to the global 3D model, image processor 106 determines that flexible medical device 102 has to be moved backward to a location within colon 110, such that the new local 3D model includes topographical features 156 and 160 in addition to topographical features 154, 158, and 162, and excludes topographical features 222 and 224. Hence, image processor 106 produces an output via user interface 108 to direct the user to move back flexible medical device within colon 110 in a direction designated by an arrow 228, until image processor 106 identifies and registers the local 3D model which corresponds to segment 150 (FIG. 2), according to the global 3D model. Once this identification and registration procedure is performed, the user can continue to advance flexible medical device within colon 110, toward target region 122 (FIG. 1).

With reference to FIG. 5, a local 3D model of a region 250 of colon 110, which is based on topographical features 158, 160, 162, 252 and 254, is referenced 256. In order to enable the user to advance flexible medical device 102 within colon 110 toward the next local 3D model, image processor 106 has to identify local 3D model 256.

It is noted that the global 3D model includes information respective of the order of successive segments respective of each region of colon 110. Hence, image processor 106 is aware of the segment of a region of colon 110, which immediately follows a preceding region thereof.

Local 3D model 256 includes a portion of topographical feature 158, and topographical features 160, 162, 252, and 254 in their entirety. In order to enable image processor 106 to identify the local 3D model respective of region 250, this local 3D model has to include topographical features 154, 156, 158, 160, and 162 in their entirety (FIG. 2), and exclude topographical features 252 and 254. For this condition to be satisfied, image processor 106 determines that the user has to twist flexible medical device 102 counterclockwise from the viewpoint of the user. Image processor 106 produces an output for the user via user interface 108, accordingly.

With reference to FIG. 6, a local 3D model of a region 280 of colon 110, which is based on topographical features 154, 158, 162, 202, 222, 224, and 252, is referenced 282. In order to enable the user to advance flexible medical device 102 within colon 110 toward the next local 3D model, image processor 106 has to identify local 3D model 282.

Local 3D model 282 includes a portion of each of topographical features 154, 158, and 252, and topographical features 162, 222, 224, and 202 in their entirety. In order to enable image processor 106 to identify and register the local 3D model respective of region 280, this local 3D model has to include topographical features 154, 156, 158, 160, and 162 in their entirety (FIG. 2), and exclude topographical features 202, 222, 224, and 252. For this condition to be satisfied, image processor 106 determines that the user has to twist flexible medical device 102 counterclockwise from the viewpoint of the user, and move flexible medical device 102 backward within colon 110. Image processor 106 produces an output for the user via user interface 108, accordingly.

Reference is now made to FIG. 7, which is a schematic illustration of a method for operating the system of FIG. 1, operative according to another embodiment of the disclosed technique. In procedure 310, an initial stereoscopic image of an initial region of a flexible organ is acquired, and an initial local 3D model of the initial region is reconstructed, according to the initial stereoscopic image. With reference to FIG. 1, stereoscopic image acquisition device 104 acquires a stereoscopic image of inner wall 124 of colon 110, at anus 120 of colon 110. Image processor 106 reconstructs a local 3D model respective of anus 120, according to the stereoscopic image of anus 120.

In procedure 312, the initial local 3D model is identified and registered with an initial segment of a previously acquired global 3D model of the flexible organ. With reference to FIG. 1, image processor 106 identifies and registers the local 3D model of anus 120, with an initial segment of the global 3D model, respective of anus 120.

In procedure 314, a successive stereoscopic image of a successive region of the flexible organ is acquired, and a successive local 3D model of the successive region is reconstructed, according to the successive stereoscopic image. With reference to FIGS. 1 and 3, stereoscopic image acquisition device 104 acquires a stereoscopic image of region 190 of colon 110, and image processor 106 reconstructs local 3D model 192 respective of region 190.

In procedure 316, the successive local 3D model is identified and registered with a successive segment of the previously acquired global 3D model. With reference to FIGS. 1, 2, and 3, image processor 106 identifies and registers local 3D model 192, according to segment 150 of the global 3D model corresponding to region 190 of colon 110. With reference to FIG. 4, image processor 106 determines that local 3D model 226 includes only a portion of topographical features respective of segment 150 (i.e., topographical features 154, 156, 158, 160, and 162). Therefore, image processor 106 produces an intermediate output via interface 108, for the user to move flexible medical device 102 back within colon 110, in direction of arrow 228. At this stage, the method returns back to procedure 314. In case image processor 106 succeeds to identify and register local 3D model 192, image processor 106 produces no output, and the method proceeds to procedure 318.

In procedure 318, a target region of interest is detected, by identifying the topography of that target region from the previously acquired global 3D model, in the successive local 3D model. With reference to FIGS. 1 and 2, once image processor 106 identifies local 3D model 192, image processor 106 checks whether the topography of the region corresponding to local 3D model, matches that of target region of interest 122. If there is a match, then image processor 106 produces a notification to indicate that target region of interest 122 has been detected (procedure 320). In case there is no match, the method returns back to procedure 314.

System 100 can also include an electromagnetic position and orientation sensor, for enhancing the overall accuracy of the system, by determining the position and orientation of flexible medical device 102 throughout the medical operation, relative to the body of the patient. The system achieves this by adding the spatial measurements of the electromagnetic sensor to the spatial measurements of the stereoscopic analysis, using for example, a Kalman filter.

The technique described herein above, can also be applicable if the medical device is a capsule, swallowed by the patient. The capsule includes a stereoscopic image acquisition device. As the capsule advances down the intestines of the patient, the stereoscopic image acquisition device acquires stereoscopic images of the intestines, including the colon of the patient. The stereoscopic image acquisition device can be a fish-eye camera, detecting stereoscopic images of the entire circumference of the inner wall of the colon. The capsule can include a memory unit for storing the acquired stereoscopic images, or a transmitter, for transmitting the acquired stereoscopic images to the image processor. The image processor reconstructs a local 3D model according to the stereoscopic image, and matches the local 3D model with a global 3D model of the colon, as described herein above.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow. 

1. Method for navigating a flexible medical device within a flexible organ of the body of a patient, toward a target region of interest of an inner wall of the flexible organ, by employing a previously acquired global three-dimensional (3D) model of the flexible organ, the method comprising the procedures of: acquiring an initial stereoscopic image of an initial region of said flexible organ, and reconstructing an initial local 3D model of said initial region, according to said initial stereoscopic image; identifying and registering said initial local 3D model with an initial segment of said previously acquired global 3D model; acquiring a successive stereoscopic image of a successive region of said flexible organ, and reconstructing a successive local 3D model of said successive region, according to said successive stereoscopic image; identifying and registering said successive local 3D model, with a successive segment of said previously acquired global 3D model; detecting said target region of interest by identifying a topography of said target region of interest according to said previously acquired global 3D model, in said successive local 3D model; and producing a notification to indicate that said target region of interest is detected, when said target region of interest is detected.
 2. The method according to claim 1, further comprising the procedure of producing at least one intermediate output, to indicate at least one corrective movement of said flexible medical device, and repeating said procedure of acquiring said successive stereoscopic image, when said procedure of identifying and registering said successive local 3D model fails.
 3. The method according to claim 1, further comprising the procedure of repeating said procedure of acquiring said successive stereoscopic image, when said procedure of detecting fails.
 4. The method according to claim 1, further comprising the procedure of displaying a 3D image of said target region of interest.
 5. The method according to claim 1, wherein said flexible organ is selected from the list consisting of: colon; esophagus; bronchus; small intestine; urinary tract; kidney; uterus; stomach; spinal canal; blood vessel; and joint.
 6. The method according to claim 1, wherein said flexible medical device is selected from the list consisting of: colonoscope; endoscope; bronchoscope; cystoscope; nephroscope; gastroscope; and arthroscope.
 7. Method for navigating a capsule within a flexible organ of the body of a patient, toward a target region of interest of an inner wall of the flexible organ, by employing a previously acquired global three-dimensional (3D) model of the flexible organ, the method comprising the procedures of: acquiring an initial stereoscopic image of an initial region of said flexible organ, and reconstructing an initial local 3D model of said initial region, according to said initial stereoscopic image; identifying and registering said initial local 3D model with an initial segment of said previously acquired global 3D model; acquiring a successive stereoscopic image of a successive region of said flexible organ, and reconstructing a successive local 3D model of said successive region, according to said successive stereoscopic image; identifying and registering said successive local 3D model, with a successive segment of said previously acquired global 3D model; detecting said target region of interest by identifying a topography of said target region of interest according to said previously acquired global 3D model, in said successive local 3D model; and producing a notification to indicate that said target region of interest is detected, when said target region of interest is detected.
 8. The method according to claim 7, further comprising the procedure of repeating said procedure of acquiring said successive stereoscopic image, when said procedure of detecting fails. 